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R W Chambers

Publications and source records attributed to R W Chambers.

At least 37 records · Page 2Linked to original sources
PubMed1977

Bisulfite-induced C changed to U transitions in yeast valine tRNA.

The reaction of yeast tRNAVallab with NaHSO3 at 25 degrees and pH 5.8 has been studied. Six reactive residues have been located. C-17 in loop I is the most reactive (51% conversion) and C-73 in the first base pair of the acceptor stem the least reactive (8%). Three of the remaining reactive residues (C-39 in loop II, C-75 and C-76 near the acceptor stem) react to the same extent (36 to 38%) under the conditions of the experiment. C-37 in the anticodon reacted to a lesser extent (28%) than C-39 (36%), located just 2 residues away in the anticodon loop. No other changes were detected, but kinetic data suggest one or more additional residues may react very slowly. The C changed to U change in the anticodon (iac changed to iau) is a missense change (Val changed to Ile). Both mechanistic considerations and experimental data from the literature show that HSO3--induced deamination of cytosine residues occurs only at unstacked residues. We interpret the quantitative changes in tRNAVal to indicate that C-17 spends a large portion of its lifetime in an unstacked conformation. The stacking lifetimes of C-37, C-39, C-75, and C-76 seem to be similar but not identical. All other cytidine residues are much more tightly stacked. These results are consistent with the folded cloverleaf models that have been proposed from x-ray diffraction studies of yeast tRNAPhe. Residues C-46, C-49, C-57, and C-61, which are present in the single-stranded regions of the unfolded cloverleaf structure, do not react, suggesting that they are tightly stacked in solution under the conditions of this experiment. The data also suggest that anticodon-loop conformations other than the extremes with five bases stacked on either the 3' or 5' portion of the anticodon stem exist in solution and that the anticodon loop is flexible.

Base Sequence↗
PubMed1977

Type specificity and use of human sera for rapid typing of herpes simplex virus isolates by an indirect peroxidase-labeled antibody technique: a comparison with three other methods.

Human sera from patients showing seroconversion following a primary herpes simplex virus type 1 (HSV-1) or HSV type 2 (HSV-2) infection, as well as 19S and 7S fractions obtained from the same sera, have been used for typing 191 HSV isolates by an indirect peroxidase-labeled antibody (PLA) method. Typing has also been performed on all of the isolates using a microneutralization (MN) and the indirect hemagglutination (IHA) inhibition test. Furthermore, 30 isolates have been typed by a plaque method. Results obtained with the PLA method was in complete agreement with those of the other two procedures. The PLA method is rapid and simple, offers easy interpretation and a permanent record of results.

Antibody Specificity↗
PubMed1977

Techniques for typing Herpesvirus hominis antibody: a comparison of inhibition of peroxidase-labelled antibody staining with inhibition of indirect haemagglutination and with microneutralisation.

A new technique based upon the inhibition of the peroxidase-labelled antibody staining (PLAS) has been used to type Herpesvirus hominis (HVH) antibodies in four groups of human sera taken from patients with one or both types of HVH infection and in mixtures of different proportions of type 1 and type 2 antisera. The results were compared with those of the microneutralisation (MN) test and the indirect haemagglutination (IHA) inhibition test. The sensitivity and specificity of the three methods were identical for sera containing only one type of HVH antibody. The MN test was slightly more sensitive than the other tests for detecting small amounts of HVH-1 antibody mixed with large amounts of HVH-2 antibody. Nevertheless, the PLAS inhibition technique was far more rapid and it would seem a satisfactory alternative to the IHA inhibition test for HVH antibody typing.

Antibodies, Viral↗
PubMed1977

Rapid detection of human cytomegalovirus and herpesvirus hominis IgM antibody by the immunoperoxidase technique.

Immunoglobulin M (IgM) to human cytomegalovirus (CMV) and herpesvirus hominis (HVH, types 1 and 2) has been searched for in a group of patients with congenital and recent CMV and HVH infections and also in a group of patients with remote CMV and recurrent HVH infections, using the immunoperoxidase antibody technique (IPA) as compared to a technique using sucrose density gradient differential centrifugation. Both techniques detected the same positive samples. High IgM antibody titers (1:32-1:512) were observed in all cases of primary CMV and HVH infection, whereas low titers (1:8-1:16) were found in congenital infections. The IPA technique is sensitive, specific and useful for rapid diagnosis of recent and congenital CMV and HVH infections.

Adult↗
PubMed1976

The immunoperoxidase technique for rapid human cytomegalovirus identification.

Sixteen cytomegalovirus (CMV) isolates from both ill and healthy patients were identified by the immunoperoxidase technique (IP). CMV detection was accomplished by direct examination of the primary isolate using either direct (DIP) or indirect immunoperoxidase (IIP) techniques. In thirteen of the isolates, confirmation of identification was achieved by indirect immunofluorescence (IFA) and by demonstration of herpes particles by electron microscopy (EM). Further, in four cases of non-CMV alterations in the tissue culture which might be confused with actual infection, the IP test was negative as were the confirmatory tests. The IIP is preferred over the DIP test since the latter shows a certain amount of background stain of uninfected cells. Tissue culture cells showing focal CMV cytopathic effect contained both nuclear and cytoplasmic inclusions stained by IP technique. Nonspecific staining was associated with cytoplasmic inclusion bodies. The IP technique can detect individual cell CMV infection at 24 hours when EM reveals only unenveloped viral particles. It is sensitive, specific, and allows direct identification of infected cells in the primary isolate in as little as 90 minutes. Furthermore, it can be performed in standard isolation tissue culture tubes, whereas IFA requires the transfer of the infected cells onto slides or the routine use of Leighton tubes.

Adult↗
PubMed1976

Rubella antibody assay by the immunoperoxidase technique: comparison with the hemagglutination inhibition test for determination of immune status.

The rubella immune status of 128 young women was determined with two assays for rubella antibody, the immunoperoxidase technique and the hemagglutination inhibition test. Comparison of the results of these techniques showed agreement in 125 cases (110 positive and 15 negative). Positive results were obtained for one woman only by the immunoperoxidase assay and for two women only by the hemagglutination inhibition test; all three of these women had a minimal titer of rubella antibody of 1:16. The sensitivity of the immunoperoxidase test was comparable to that of the hemagglutination inhibition test, and the specificity of the former test was verified. The peroxidase-labeled antibody technique is easier to perform than the hemagglutination inhibition test and is less time-consuming since sera do not require prior treatment and results can be obtained in as little as 90 min.

Antibodies, Viral↗
PubMed1976

Immunoperoxidase technique for detection of antibodies to human cytomegalovirus.

The indirect immunoperoxidase antibody technique (IPA) has been applied to determine immunoglobulin (Ig)G to humans cytomegalovirus (CMV) antibodies in 114 blood donor sera, four cases of congenital cytomegalic inclusion disease, and four cases of acquired CMV infection. The results have been compared with those obtained with the CMV complement fixation (CF) test and indirect fluorescent antibody technique (IFA) for broad spectrum CMV antibody (sigmaAb) detection. IgG antibody has been detected by both CF and IPA. In healthy adult people IPA titers are usually higher than CF titers. In addition, IFA sigmaAb titers are generally higher than CF titers. Some sera negative by CF and IPA are positive at low dilutions by IFA sigmaAb antibody determination, due to the detection of small amounts of IgA or noncomplement-fixing IgG. Nonspecific results seem unlikely, since only nuclear inclusion fluorescence was interpreted as specific, as demonstrated by blocking tests. In acute CMV infection, the IFA sigmaAb and IPA IgG titers are essentially the same, except during the first weeks of infection, when IFA titers are higher and IgM is detectable. No cross-reactivity with other herpes group viruses, herpes simplex and varicella-zoster, was observed. Although some problems of nonspecific staining of cytoplasmic inclusions are shared by both methods, the IPA technique seems to possess the same degree of sensitivity and specificity as the IFA technique, but interpretation is easier and various procedural steps can be delayed without the technical problems associated with fluorescence microscopy.

Adult↗
PubMed1976

Varicella-zoster plaque assay and plaque reduction neutralization test by the immunoperoxidase technique.

A new plaque assay for the quantitation of varicella-zoster virus and a plaque reduction neutralization test for the determination of neutralizing antibody titer have been developed using the indirect immunoperoxidase technique. As compared with the classical plaque assay using a solid overlay, the test gives earlier results since plaque counting can be performed on day 3 after the inoculation of cell cultures. In six patients with zoster infection, neutralizing antibody titers ranged from 1:20 to 1:40 before the onset of infection and reached high levels (1:320 to 1:5,120) during the convalescent phase of the disease. Complement-fixing (CF) titers were all negative (less than 1:8) in prezoster serum samples from the same patients and ranged from 1:128 to 1:2,048 in the convalescent-phase sera. In the two cases in which late serum samples were available, neutralizing antibody titers matched the preillness levels, whereas CF titers dropped to undetectable levels. Neither neutralizing nor CF antibody was detected in two sera from individuals with no history of varicella-zoster infection. No differences in virus titers or neutralizing antibody titers were observed between the immunoperoxidase and the classical plaque assays. The appropriate characterization of reagent specificity is required before routine application of the test.

Antibodies, Viral↗